Dosimetric comparison of high dose rate interstitial brachytherapy and stereotactic body radiotherapy as alternative treatment methods for advanced-stage cervical cancer.

Purpose.High-dose-rate interstitial brachytherapy (HDR-IBT) is an essential component of curative treatment for locally advanced cervical cancer, but it is invasive and resource-intensive. Alternative boost techniques are needed when brachytherapy is not feasible. This study compares the dosimetric performance of stereotactic body radiotherapy (SBRT) and Syed-based HDR-IBT to evaluate the potential role of SBRT as a non-invasive boost modality.Materials and Methods.Eighteen patients with stage III-IV cervical cancer previously treated with external beam radiotherapy (EBRT) (45 Gy/25 fx ± nodal boost) followed by Syed HDR-IBT (28 Gy/4 fx) in our clinic were retrospectively analyzed. For each patient, SBRT plans prescribing 28 Gy in 4 fractions were generated on EBRT computed tomography images using fused Syed contours. Dosimetric parameters for targets and organs-at-risk (OARs), such asD98,D90, mean dose, maximum dose,D2cc,D1cc, were compared using the Wilcoxon signed-rank test.Results.For the high-risk clinical target volume (CTV_HR), HDR-IBT provided significantly superior coverage: mean 27 GyD98and 32 GyD90(Syed) vs. mean 25 GyD98and 29 GyD90(SBRT) (p= 0.04 andp< 0.001). For the intermediate-risk CTV, SBRT plans achieved significantly better coverage: mean 18 GyD98and 22 GyD90(SBRT) vs. mean 14 GyD98and 18 GyD90(Syed) (p< 0.001 for both). OAR doses were largely comparable between the two modalities, except that HDR-IBT resulted in significantly lower mean bladder dose and improved bowel sparing, whereas SBRT yielded significantly lower bladder maximum dose and reduced rectumD2cc. Overall, SBRT exhibited greater low-dose spread to surrounding tissues, while HDR-IBT produced higher intratumoral dose hot spots.Conclusion.HDR-IBT remains superior for CTV_HR dose escalation, but SBRT can achieve acceptable target coverage and OAR sparing when brachytherapy is not feasible. SBRT may serve as a practical alternative for selected patients who are medically inoperable, anatomically unsuitable, or lack access to brachytherapy services. Prospective studies are needed to optimize SBRT planning strategies and define appropriate patient selection criteria.